1. Field of the Invention
The present invention generally relates to a multimedia playing method and apparatus, and more particularly, to a multimedia playing method and apparatus which can shorten the playing delay and optimize the planning of a buffer memory and the shock protection time.
2. Description of Related Art
A walkman compact disc (CD) player or a car CD player is distinct from a general CD player in that the walkman or the car CD player usually operates in a vibratile environment. An optical pickup head of the CD player may not be able to read data correctly in a vibratile environment and accordingly the playing becomes discontinuous. Typically, there are two kinds of solutions which may be adopted to prevent the playing discontinuity. One is to enhance the shock endurance mechanism of the CD player. The other is to introduce a buffer memory in which the CD player stores a part of a soundtrack to be played (determined by the size of the buffer memory, for example, 40 seconds of the soundtrack) into the buffer memory. In operation, the CD player directly reads and plays the soundtrack from the buffer memory. When the optical pickup head of the CD player cannot read data because of some shocks, the CD player can still play the soundtrack from the buffer memory. As a result, playing discontinuity is avoided.
Along with the development of CD players, a CD player nowadays is capable of playing compressed soundtracks, such as MP3 files, adaptive predictive encoding (APE) files, or free lossless audio codec (FLAC) files. Generally speaking, the mp3 files may have a compression rate of 1:10. Even though compression may result in loss of audio quality, the MP3 format is still popular for its “convenient size”. The APE and FLAC files are compressed through lossless compression techniques, therefore, they also take an important part in the market. A compressed soundtrack has a smaller file size. Taking the MP3 format with a transmission rate of 128K bit/s and a sampling frequency of 44100 Hz as an example, the file size of a 5-minute soundtrack is only about 4 to 5 M bytes. Thereby, several MP3 files can be stored into a buffer memory and accordingly a shock protection effect sometimes may up to hundreds of seconds.
However, a CD player with a buffer memory may still produce some problems. For example, when a CD player is playing a first soundtrack on a CD (i.e., parts of the first soundtrack is stored in the buffer memory of the CD player) and if a user wants to play another soundtrack and presses the “next track” button, the CD player has to erase the buffer memory first and then start to store parts of the selected soundtrack into the buffer memory. Even though the capacity of the buffer memory is large enough for storing more than one soundtrack, e.g. storing the first, the second and the third soundtracks when playing the first soundtrack, if the user wants to play a fifth soundtrack, the CD player still needs to erase the buffer memory and then start to store the fifth, the sixth and the seventh soundtracks into the buffer memory. It results in playing delay during the erasing and storing operation. Similarly, a mini disc (MD) player has the problem as well.
Accordingly, a disc player having a disc and a cache memory is disclosed in U.S. Pat. No. 6,934,812. When a user selects a file, the file is divided into an initial part and a remaining part. At playing, the disc player reads the initial part of the file and directly plays it without storing it into the cache memory. As a result, the delayed time for playing the file is shortened. Moreover, while playing the initial part, the player retrieves the remaining part of the file to store into the cache memory, which means the remaining part has to go through the cache memory to be played.
A player is disclosed in U.S. Pat. No. 7,042,813, wherein when playing a soundtrack, the player retrieves the initial parts of a plurality of soundtracks and stores these initial parts into a buffer memory. However, the initial parts of the soundtracks stored in the buffer memory are deleted after they are played, and accordingly, the player has to constantly detect whether the part which is not yet played in the buffer memory is lower than a threshold.
A disc player is disclosed in U.S. patent No. US20070156962, wherein a user defines a playlist, and each file on the playlist is divided into an initial part and a remaining part. These initial parts (2% of the file size) are stored into a buffer memory to avoid the playing delay problem.